Radiation therapy can involve administering a dose of radiation to a human or animal subject. Careful planning can help ensure that the radiation reaches a target region of interest, while avoiding one or more nearby regions that are not expected to benefit from radiation and that may be impacted by side-effects of such radiation.
Three-dimensional (3D) imaging data can be used to plan radiation treatment. Such 3D imaging data can be obtained, for example, from a magnetic resonance (MR) or computed tomography (CT) imaging device. The 3D imaging data can include voxels representing imaging data of various densities. For example, 3D voxel data of tissue within the subject will represent a higher density than voxels representing air outside of the subject. Voxels corresponding to air within a body cavity (e.g., within the bronchial tubes, for example, will also exhibit less density than surrounding tissue. Bone tissue voxels will have a higher density than softer tissue voxels.
One technique for delivering radiation to a desired region of interest within a subject can involve generating photons. For example, photons incident into tissue can generate free electrons within the tissue. Free electrons can follow a complex trajectory within the tissue, particularly under the influence of a magnetic field, such as can be present when radiation therapy is administered when the subject is within the magnetic field of an MR imaging device.